GPS Survey of the salar de Uyuni, Bolivia, for Satellite Altimeter Calibration
Abstract
The salar de Uyuni, a 100km x 100km salt flat in the Andean Altiplano of southern Bolivia, is the largest dry lake on Earth. The size, high albedo and remarkable flatness of the salar make it an ideal reference surface for satellite-based altimeters - in particular, the Geoscience Laser Altimeter System (GLAS) to be flown on the Ice, Cloud and Land Elevation Satellite (ICESat) - especially with regard to range measurements and waveform analysis of return signals. A simple reference surface such as the salar can be mapped by ground-based surveying, although the sheer size of the area requires adaptations to standard survey techniques. We describe a survey of the salar de Uyuni carried out with car-mounted kinematic GPS over a seven-day period in September 2002. We divided the salar surface into a number of survey grids that were driven in multiple directions to yield redundant measurements and corresponding error statistics at grid crossover points. Adjacent grids were overlapped so we could also determine errors between grids and over multi-day time periods. In addition, we set up five fixed GPS sites on the salar to serve as local survey control in post-processing. These fixed sites will be used to map ionospheric effects and interpolate them to the roving GPS receivers. If successful, this will allow reprocessing of GPS solutions using L1 data only, with a corresponding reduction in noise compared to solutions using the standard ionosphere-free LC combination. We present our surveyed topography of the eastern half of the salar de Uyuni, comparing it to previously-published elevation measurements and to the best geoid model available for the region. We show the close relationship between the topography of the salar and the shape of the geoid, a result we had expected since the salar is flooded each austral summer to an almost uniform depth. We also demonstrate knowledge of the surface height of the salar to within the measurement error specified for the GLAS instrument.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFMOS52A0193B
- Keywords:
-
- 1204 Control surveys;
- 1625 Geomorphology and weathering (1824;
- 1886);
- 1640 Remote sensing